In this paper, we propose a method to analyze the differences in the motions of gaze and hands between skill levels in assembly tasks. The method quantizes the positional information of the gaze and hands into eighteen areas and converts the positional information of into a code. Next, it calculates the occurrence frequency of pairs of codes. Then, it generates co-occurrence histograms, called “Gaze/motion integration features,” using the occurrence frequency. We can analyze the relationship of motions between the gaze and hands using these features. The results of an analysis of a skill improvement process are that the non-dominant hand of an “elementary level” stays in two areas, and the non-dominant hand of an “intermediate level” moves to five areas. Therefore, humans can move their non-dominant hand more efficiently at the “intermediate level” than at the “elementary level.” In addition, we found that the gaze of the “intermediate level” moves to eight areas, and the gaze of the “expert level” moves to three areas. Therefore, we found that the gaze of the “expert level” remained at the center of the workbench.